Heat Pipe Test Research Articles

Evaluation of start-up characteristics for heat pipe-cooled nuclear reactor coupled with recuperated open-air brayton cycle using hardware-in-the-loop

The heat pipe-cooled nuclear reactor (HPR) holds great importance for the low-carbon transition period and can be applied flexibly and stably in numerous scenarios. However, studies on the dynamic performance of the HPR coupled with the open-air Brayton cycle (OBC) are scarce, and achieving a balance between economy and accuracy has proven challenging. In this work, a hardware-in-the-loop (HIL) method is proposed and implemented for the coupled HPR-OBC prototype by combining the benefits of experimental measurements and numerical simulations. A sodium heat pipe test rig is heated in the real world, while neutronics and OBC dynamics are synchronously solved using Simulink models. A transient HIL test lasting for 12000 s is conducted to explore the start-up process of HPR-OBC. The coupled system successfully reaches steady-state by regulating reactivity and shaft speed. The results indicate a strong coupling effect between the shaft speed, the heat transfer rate of the heat pipes, and the air flow state in the OBC. The turbomachine operates within reasonable regions and no surge or choke phenomena occur. The final reached OBC efficiency is 20 %, and the generated electricity power output is 0.16 MWe.

Heat generation and transfer simulation of a high temperature heat pipe under induction heating based on a coupled model

High temperature heat pipes are highly efficient heat transfer devices, and induction heating is often utilized in their performance tests. However, issues exist in evaluating the equivalence between induction heating and surface heating encountered in typical application scenarios, and in quantifying the accurate input heat flux of induction heating. In order to identify the key influencing factors and investigate their effects on heat generation and transfer within high temperature heat pipes under induction heating, a finite element thermal-electrical coupled model is developed based on the pseudo wick thermal conductivity model and electromagnetic theory. The effects of frequency (10 kHz, 100 kHz, 300 kHz), loaded current (10 ∼ 890A), cooling coefficient (10 ∼ 250Wm-2K−1) and temperature (300 ∼ 1000 K) are investigated. Over 98% of the induction heat is found to be generated in the evaporator section, with a considerable proportion generated in the annular channel (38 ∼ 52%) and the capillary wick (23 ∼ 26%) at low frequency (10 kHz). The wall temperature of the evaporator section is slightly lower than the temperature of the annular flow channel or even the capillary wick at weak cooling boundary conditions (<130Wm-2K−1@10 kHz, <50Wm-2K−1@100 kHz, <30Wm-2K−1@300 kHz). Quantitative calibration formulas of induction heat are established in relation to frequency, current, and temperature via two sets of quadratic polynomial fitting. The results can be used as reference for design and evaluation of transient and steady-state tests of heat pipes under induction heating.

Design and Thermal-Hydraulic Performance Analysis of a Low-Temperature Heat Pipe Test Facility

Interest in heat pipe microreactors (HPMRs) has recently grown due to several unique advantages compared with other reactor types. These compact and mobile reactors are expected to find applications in a variety of fields to provide carbon-free power in remote or off-grid locations. Experimental work is needed to aid and expedite the design and licensing of future HPMRs, especially on the validation of heat pipe performance as key heat transfer components. A Low-Temperature Heat Pipe Test Facility (LTHPF) was designed and constructed according to previously developed scaling laws to bypass the difficulties of experimenting with liquid-metal working fluids by using surrogate fluids. The design, instrumentation, and experimental capabilities of the facility are described. The testing conditions, including various operating limits and the ranges of the nondimensional parameters used for scaling analysis, are reported. It is found that certain nondimensional parameters could yield a wide range over the operating conditions, whereas some showed minimal variation when water was used as the working fluid. Last, the performance of several types of wicks, including the annulus-screen, groove-screen, and wrapped-screen designs, were investigated for applications in the LTHPF. It is observed that the groove-screen wick structure provided slight improvement in capillary limits at higher temperatures and that the wrapped-screen wick yielded lower capillary limits due to the absence of a low-resistance flow path for the liquid.

Experimental investigation and mechanism analysis: Effect of concentration and temperature on the heat transfer characteristics of novel MWCNT-mustard oil nanofluid

ABSTRACT. The bio-oils as alternative lubricating fluid are potential solution for the automotive and industrial mechanical systems. The development of novel renewable and non-toxic bio-oils with better heat transfer distinctiveness will strengthen the economy of farmers in the agricultural based countries. The most innovative approach to improve the heat transfer characteristics of bio-oils is converting it into nanofluids by dispersing nanomaterials which has extremely high heat transfer characteristics. In this study, MWCNT-Mustard oil nanofluids were formulated through ultrasonication and their dispersion stability was estimated through Zeta-potential technique. The thermal stability of the MWCNT-Mustard oil nanofluids are estimated through thermogravimetric analysis and concentration and temperature dependent density, thermal conductivity and specific heat capacity of MWCNT-Mustard oil nanofluids are also determined and their characteristics are discussed. The heat transfer characteristics of MWCNT-Mustard oil nanofluids observed through the heat pipe test rig at different inlet temperatures, mass flow rate of nanofluids and Reynolds number. The results exhibits that the dispersion of MWCNT enhances the heat transfer characteristics of MWCNT-Mustard oil nanofluids.&#x0D; &#x0D; KEY WORDS: Non-toxic bio-oils, Nanomaterials, Nanofluids, Thermogravimetric analysis, MWCNT, Mustard oil&#x0D; Bull. Chem. Soc. Ethiop. 2022, 36(3), 675-686. &#x0D; DOI: https://dx.doi.org/10.4314/bcse.v36i3.16

A review on data centre cooling system using heat pipe technology

Heat pipe, a high efficient, cost effective and reliable device, is considered one of the most promising passive technologies for cooling data centres. Aiming to provide comprehensive information and focused perspective on heat pipe system for cooling data centres, the literature reviewed in this review is obtained from the Web of Science by searching the topic “heat pipe” and “data centre” conducted on Sep. 1, 2019 for the decade from 2009 to 2018. In this paper, a comprehensive review on heat pipes for use in data centre cooling systems will be carried out, starting from the working principle, heat transfer analysis and applications. The review works will be analysed in terms of the system research methodology, energy performance evaluation, and IT tasks. From the system research methodology, the heat pipe structure, simulation and testing analyses were conducted. From the energy performance evaluation, the energy consumption, energy recovery and energy saving analyses were studied. From the IT tasks, the avoidance of hot spots and thermal management in the data centres were analysed. The opportunities for further works are revealed including: developing new and efficient data centre cooling systems employing advanced technology; optimising the heat pipe structure for the data centre cooling systems; testing the data centre cooling systems under actual conditions; and evaluating the economic feasibility and market potential of the data centre cooling systems. This review provides the guidelines for the development of data centre cooling system based on the heat pipe.

Foundations for a Fission Battery Digital Twin

As the nuclear industry moves toward construction of microreactors and next-generation reactors, these efforts pose new challenges. A digital-twin tool will reduce costs and risk through integration of the disparate systems used in the design, construction, and operation of these reactors. Recent investments at Idaho National Laboratory (INL) in open-source digital engineering and multiphysics framework development provide a foundation from which to create and evaluate a digital twin for nuclear reactors. This digital-twin tool will use the Single Primary Heat Pipe Extraction and Removal Emulator (SPHERE) and Microreactor AGile Non-nuclear Experimental Testbed (MAGNET) as case studies to develop a digital twin with both single and 37 heat pipe test articles. The digital twin will provide the capabilities of remote monitoring and unattended operation (autonomous control) of these systems. A digital twin is a digital replica of an operating asset that can display data received from live sensors, update a physics model for the asset with the received data, compute predictive results of operational status with artificial intelligence (AI) to aid in optimizing asset use, and apply asset control accordingly. This twin will be developed through integration of the open-source technologies Deep Lynx (a data-warehouse technology) and the Multiphysics Object-Oriented Simulation Environment (MOOSE), physical-asset sensors, and physical-asset controls. Specifically, the general AI will successfully predict the events described as MAGNET heat pipe article test cases (such as heat pipe failure) using integrated data from the MAGNET sensors and physics-based models, including developed meta models. The integration of open-source INL software and AI assets with sensor data from a test bed will lead to a repeatable framework and guide for the creation of future digital twins. The team will also perform AI model training and experimentation to determine what models and features are most important to enable intelligent, autonomous control as well as to evaluate and determine best practices for digital-twin cybersecurity.

Comparison tests of loop heat pipes with flat evaporators of different types

Comparison tests have been conducted on a flat-oval evaporator with a longitudinal replenishment of the evaporation zone with a working fluid (ELR) measuring 110 × 50.5 × 10 mm3 and a flat disk-shaped evaporator with opposite replenishment (EOR) 50 mm in diameter and 19 mm in thickness. The evaporators have been tested as parts of copper-water loop heat pipes (LHPs) with identical design parameters, with a heat source of 40 × 40 mm2 at a heat sink temperature of 40 °C. It is shown that an LHP with an ELR has a significantly lower operating temperature in the whole range of heat loads. The maximum heat load of the device with an ELR was 800 W at an evaporator temperature of 109.5 °C and with an EOR it was 600 W at a temperature of 121.1 °C. The corresponding thermal resistances of the evaporators were 0.025 °C/W and 0.046 °C/W. At a nominal heat load of 300 W the ELR temperature was 70.2 °С and the EOR temperature 87.4 °С. The devices were designed for use in energy-efficient cooling systems for high-power electronics. A computer simulation of heat exchange processes in the evaporators was carried out taking into account parasitic heat flows into the compensation chamber.

Hysteresis phenomena in flat-type loop heat pipe

Testing of loop heat pipes showed that the heat-load dependence of the operating temperature was not always unambiguous. It may have hysteresis phenomena. The temperature hysteresis had a certain relationship with previous history of the power variation, and also related to the initial parameters of the loop heat pipes. It has been found that the temperature hysteresis of the loop heat pipes was related to the gas-liquid distribution in the compensation chamber which depended on the interaction between heat leak of evaporator and the reflux liquid from condenser. The temperature of the loop heat pipes evaporator rose with the gas phase in the compensation chamber increased.

Experimental and Numerical Analysis of Composite Wick Heat Pipes using Ethanol

Warmth pipes come convenient now-a-days as they work with most noteworthy warmth conductance contrasted with some other method of warmth move and accessible over wide scope parameters. In the present investigation de-ionized water stream in plain thermo siphon, Sintered Copper wick and Helical scored heat pipes with synchronous vanishing, adiabatic and buildup wonder are contemplated utilizing Heat pipe test gear. In this hardware warmth pipe exposed to foreordain heat load an obstruction radiator at its evaporator end water coat with controlled progression water is utilized disperse warmth vitality at condenser end. Every one temperatures are estimated necessary computations are done get rate efficiencies at different stream rates warmth inputs. The exhibition warmth funnels correlation between their efficiencies is done. The sintered copper wick structure pipe have been found capable when stood out from other two with heat inputs beginning from 50 to 800 watts evaporator 30, condenser 72, adiabatic 110, flate heat pipe width 7.6mm, thickness 3.4 mm, first dia 6mm warmth pipe holder thickness in 0.5mm working liquid ethanol wick in view prevailing Capillarity property. The varieties of evaporator and condenser surface temperatures are plotted for changing warmth information sources and stream rate changes at condenser water coat. ANSYS programming is utilized for computational investigation and exploratory outcomes are in great concurrence with the examination.

The visualized investigation on flow and heat transfer characteristics of flat-plate heat pipe with micro rectangular grooves

With the development of information technology, the heating power of data transmission equipment (mobile phones, notebook computers, data center processors, etc) continues to rise, and the high temperature failure has become a major cause of equipment damage. At present, the heat flux of high-power chips has reached 2 ´ 106 W/m2. Therefore, the traditional single-phase heat transfer is unable to meet the heat dissipation requirements of new data equipment, and more efficient heat exchange methods are urgently needed to ensure the normal operation of the equipment. As a highly efficient phase change heat transfer element, the thin plate grooved heat pipe is researched in the order of millimeters or even micrometers. Therefore, flat grooved heat pipes simultaneously satisfy the heat dissipation and packaging requirements of high power data transmission equipment, and thus have been extensively studied. In the present study, the phase change characteristics and heat transfer performance of flat-plate heat pipes with rectangular grooves were experimentally studied. Each micro heat pipe test section consisted of twenty parallel grooves with the same total length of 90 mm. The cross-sectional area of G-400 heat pipe and G-800 heat pipe were 400 μm ´ 400 μm and 800 μm ´ 800 μm, respectively. The evaporation section, adiabatic section and condensation section had the same size of 30 mm, and vapor space height was equal to 3.6 mm. The flat-plate was sealed on its upper face with transparent plate, and the phase change phenomenon in the grooves could be observed. A high speed camera was used to visualize the phase change phenomenon in evaporation and condensation regimes. The experiments were carried out with the same cooling water temperature of 30°C under the conditions comprising the heat power range of 18–90 W and filling ratio of 150%–400%, respectively. In order to systematically investigate the performance of flat heat pipes with different dimensions of micro grooves, the analysis was focused on the heat resistance and phase change phenomenon in evaporation section and condensation section. The results showed that the heat pipe with wide grooves was able to maintain stable heat transfer performance at higher heat power, while heat pipes with narrow grooves would dry out at lower heat power. The optimal liquid filling rate of G-400 heat pipe was 400%, and the optimal liquid filling ratio of G-800 heat pipe was 150%. Furthermore, the heat transfer in the evaporation section of flat heat pipe with narrow grooves was mainly dominated by liquid film evaporation. Comparatively, the heat transfer phenomenon in the evaporation section of a heat pipe with wide grooves was affected by the liquid filling ratio. The liquid film evaporation was the main solution at low liquid filling ratio, and continuous bubble behavior was visualized in high filling ratio. In addition, the phase change behaviors in the condensation section of rectangular-grooved flat heat pipe not only occured at the gas-liquid interface, but also had droplet condensation phenomenon on the top surface of the groove rib. The cycle of condensation consisted of three stages: Droplet growth, droplet coalescence, and droplet department.

The results of comparative analysis and tests of ammonia loop heat pipes with cylindrical and flat evaporators

Comparative analysis and tests of ammonia loop heat pipes (LHPs) with a flat disk-shaped evaporator 40 mm in diameter and a cylindrical evaporator 10 mm in diameter equipped with a 40 mm × 40 mm × 12.2 mm copper interface were conducted. Both evaporators had the same heated surface 12.56 cm2 in size. The length and the diameter of the vapor line and the condenser were also equal. Tests of LHPs were conducted at +90°, 0°, −90° angles with respect to gravity and identical condenser cooling conditions at +20 °C heat sink temperature. For the cylindrical evaporator, the maximum heat load of 400 W (31.8 W/cm2) was reached at a junction temperature of 86.5 °C. For the flat evaporator, the maximum value of heat load was 320 W (25.5 W/cm2) at a junction temperature of 91 °C. For the cylindrical evaporator, the minimum value of thermal resistance of 0.064 °C/W was reached at maximum heat load. For the flat evaporator, it was 0.067 °C/W at 180 W heat load. As orientation was shifted, the value of the maximum heat load fluctuated by no more than 20–25% for both devices, while the value of the minimum thermal resistance fluctuated by no more than 4% for the cylindrical evaporator and no more than 12% for the flat one.

Infrared thermographic testing of hyperconductive flat heat pipes

Active infrared thermography has been applied for the evaluation of the internal structure and operation quality of hyperconductive flat mini heat pipes used in satellite electronics. The distribution of effective transverse thermal diffusivity in heat pipes has been obtained by means of the Parker technique to exhibit areas with low content of fluid in the porous structure. The lateral components of thermal diffusivity were determined by placing a slit mask between a flash heater and a heat pipe. Peculiarities of heat pipe operation in a working regime have been experimentally studied by placing a local heat source on the pipe surface and following the surface temperature dynamics.

Experimental and numerical investigation of contact heat transfer between a rotating heat pipe and a steel strip

A new concept for energy efficient annealing of steel strip comprises of multiple rotating heat pipes. Each heat pipe extracts heat from the cooling strip which is reused to increase the temperature of the heating strip. In this context, the heat transfer between the steel strip and the rotating heat pipe is investigated. When the strip is transported over the heat pipe, gas entrains in the gap. The gas compresses into a uniform gas layer. The contact heat transfer deteriorates due to this phenomenon. A numerical model to quantify the heat transfer between the surfaces is developed. Since there is no direct way to quantify the heat transfer between two moving surfaces, the problem is divided into a gas entrainment and a heat transfer part. The model is validated with experiments executed on a rotating heat pipe test rig. The validation was made varying the strip thickness, specific tension and strip velocity. The results show a uniform gas layer forming within the first 1° of the 180° wrap angle in all cases. The heat transfer is dominated by gas conduction. Results for the uniform gas layer region yield heat transfer coefficients in the range between 4000 and 20,000 W/m2·K.

Heat pipes with variable thermal conductance property for space applications

The activities presented in this paper focus on a new approach to provide passive regulation of the electronic unit thermal regime of the MASCOT lander (DLR) onboard the NEA sample return mission Hayabusa 2 (JAXA), by using heat pipes. It provides information on the development and testing of heat pipes with variable thermal conductance in a predetermined temperature range. Such heat pipes acts as thermal switches, but their construction does not include additional elements inherent to gas loaded heat pipes (GLHP) and thermal diode heat pipes (TDHP). Copper heat pipes with metal fibrous wick were chosen as baseline design. We have obtained positive results by choosing heat carrier and structural parameters of wick (i.e. pore diameter, porosity and permeability). A rising of heat pipes thermal conductivity from 0.04 to 2.1 W/K was observed in the temperature range between -20°C…+55°C. The heat pipes transferred predetermined power not less than 10 W within the temperature range of +20°C… +55°C. These heat pipes are in flight since December 2014 and the telemetric data obtained in September 2015 showed normal operation of the thermal control system.

1D and Q2D thermal resistance analysis of micro channel structure and flat plate heat pipe

Heat pipes and two-phase heat transfer devices are widely used in electronics cooling, and the thermal resistance is a key issue to ensure the system performance and reliability. In this study, the traditional one dimensional (1D) and quasi-two dimensional (Q2D) methods were utilized to analyze the thermal resistance of the previous boiling experiments of evaporator tests with silicon (Si) and copper (Cu) micro channel structures as well as the existing flat-plate heat pipe tests with aluminum micro channels as wick structures. The temperature distributions and variations under different test conditions were collected, and the 1D and Q2D methods were applied to calculate the overall thermal resistance for evaporator tests and heat pipe tests and compared with the experimental data. The results showed that the Q2D method can predict the overall thermal resistance for the evaporator region and the whole heat pipe with a higher accuracy because the spreading resistance was significant and should be considered under small heater area (hot spot) conditions. Detailed distributions of thermal resistance and the calculated errors of each test sample under different heat loads were presented and compared. For present tests, the Q2D method can reach a lower average error (about 10%) and is recommended for calculations. Furthermore, the spreading resistance of Q2D method is further applied to calculate the selected test cases to investigate the wall thickness effects. The spreading resistance of the selected evaporator tests and heat pipe tests may decrease and increase, respectively, as wall thickness increases due to different evaporative heat transfer conditions. The present results demonstrate the applicability of the Q2D methods for both evaporator and heat pipe tests, and the present analyses can be a reference for future thermal management and electronic cooling designs.

Constructive and technological aspects of the heat flow imitator based on diamond-like films

The paper describes features of the design and manufacturing technology of a volumetric detachable heat flow imitator designed for the study of thermal characteristics and for carrying out thermal tests of heat pipes of cooling systems for electronic equipment. The authors use thin alumina ceramic plates with deposited with diamond-like films as heating elements of the imitator. Experimental results are presented on the surface temperature of heating elements and the temperature drop between the heating elements and the heat pipe in the region of the input heat flux values from 5 to 25 W. The use of the proposed heat flow imitator allows speeding up the process of research and testing of heat pipes.

Heat pipes as perspective base elements of heat recovery in heat supply and ventilating systems

Thermotechnical characteristics of heat pipes are considered as high-efficient heat-transfer devices, which can provide energy-saving technologies for heat supply and ventilating systems and for different branches of industry. Thermotechnical and working (”performance capability”) characteristics of heat pipes are investigated. By ”performance capability” of heat pipes and heat-transfer devices on heat pipes we mean the system state, where it can perform set functions and keep parameter values (thermal power, conductivity, thermal resistance, heat-transfer coefficient, temperature level and differential, etc.) within the regulations of standardized specifications. The article presents theoretical and experimental methods of «gaslock» length determination on noncondensable gases during long-lasting tests of ammonia heat pipes made of aluminum shape АS – КRА 7.5 – R1 (alloy АD – 31). The paper gives results of research of thermotechnical characteristics of heat pipes in horizontal and vertical states (separate and as a set part) while using different systems of thermal insulation. The obtained results of thermotechnical and resource tests show the advantages of ammonia heat pipes as basic elements for heat exchanger design in heating and ventilation systems.

Performance Study of Solar Heat Pipe with Different Working Fluids and Fill Ratios

This paper elaborates on the testing of solar heat pipes using different working fluids, fill ratios and tilt angles. Methanol, Acetone and water are used as working fluids, with fill ratios 25%, 50%, 75% and 100%. Experiments were carried out at 600 and 350 inclinations. Heat pipe condenser section is placed inside a water basin containing 200ml of water. The evaporator section is exposed to sunlight where the working fluid gets heated and it becomes vapour and moves towards the condenser section. In the condenser section the heat is given to the water in the basin and the vapour becomes liquid and comes back to the evaporator section due to gravitational force. Two modes of experiments are carried out: 1) using a parabolic collector and 2) using heat pipe with evacuated tubes. On comparative study, optimum fill ratio is been found to be 25% in every case and acetone exhibited slightly more efficiency than methanol and water. As far as the heat pipe orientation is concerned, 600 inclination of the heat pipe showed better performance than 350

Разработка оборудования для тестирования тепловых труб

Разработка оборудования для тестирования тепловых труб

Experimental study on heat pipe heat removal capacity for passive cooling of spent fuel pool

A loop-type heat pipe system uses natural flow with no electrically driven components. Therefore, such a system was proposed to passively cool spent fuel pools during accidents to improve nuclear power station safety especially for station blackouts such as those in Fukushima. The heat pipe used for a spent fuel pool is large due to the spent fuel pool size. An experimental heat pipe test loop was developed to estimate its heat removal capacity from the spent fuel pool during an accident. The 7.6m high evaporator is heated by hot water flowing vertically down in an assistant tube with a 207-mm inner diameter. R134a was used as the potential heat pipe working fluid. The liquid R134a level was 3.6m. The tests were performed for water velocities from 0.7 to 2.1×10−2m/s with water temperatures from 50 to 90°C and air velocities from 0.5m/s to 2.5m/s. The results indicate significant heat is removed by the heat pipe under conditions that may occur in the spent fuel pool.